Abstract Rationale Hypertrophic cardiomyopathy (HCM) is the most common cardiac genetic disorder caused by sarcomeric gene variants and associated with left ventricular (LV) hypertrophy and diastolic dysfunction. The role of the microtubule network has recently gained interest with the findings that α-tubulin detyrosination (dTyr-tub) is markedly elevated in heart failure. Reduction of dTyr-tub by inhibition of the detyrosinase (VASH/SVBP complex) or activation of the tyrosinase (tubulin tyrosine ligase, TTL) markedly improved contractility and reduced stiffness in human failing cardiomyocytes, and thus poses a new perspective for HCM treatment. Objective In this study, we tested the impact of targeting dTyr-tub in a mouse model of HCM, the Mybpc3 -targeted knock-in (KI) mice, and in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and engineered heart tissues (EHTs) deficient in SVBP or TTL. Methods and Results TTL gene transfer was tested in wild-type (WT) mice and rats and in adult KI mice. We show that i) TTL dose-dependently reduced dTyr-tub and improved contractility without affecting cytosolic calcium transients in WT cardiomyocytes; ii) TTL partially improved LV function and diastolic filling, reduced stiffness and normalized cardiac output and stroke volume in KI mice; iii) TTL induced a marked transcription and translation of several tubulins in KI mice; iv) TTL modulated mRNA or protein levels of components of mitochondria, Z-disc, ribosome, intercalated disc, lysosome and cytoskeleton in KI mice; v) SVBP-KO and TTL-KO EHTs exhibited low and high dTyr-tub levels, higher and lower force of contraction and enhanced and prolonged relaxation than in WT EHTs, respectively. RNA-seq and mass spectrometry analysis revealed distinct enrichment of cardiomyocyte components and pathways in SVBP-KO vs. TTL-KO EHTs. Conclusion This study provides evidence that reducing dTyr-tub improves function in HCM mouse hearts and human EHTs and holds promise for targeting the non-sarcomeric cytoskeleton in heart disease.

Reducing microtubule detyrosination improves heart function in HCM mice and human iPSC-engineered heart tissues